Light control for photographic-printing machines



Aprii 8, 1930.

N. is. GREEN LIGHT CONTROL FOR PHOTOGRAPHIG PRINTING MACHINES Filed Deg. $1, 19 26 2 Sheets-Sheet l lllliii? 52 2400 N BIA/812mm, 9 n, 166'1U 190 y 490 fiTTORNEYS. VOLTS 100 I05 Il0 [l5 I20 I25 v v Aprnl 8, 1930. N. B. GREEN 1,754,204 IIGHT CONTROL FOR PHOTOGRAPHIC PRINTING MACHINES Filed Dec. 31, 1926 2 Sheets-Sheet 2 f ATTORN'EYS.

Patented Apr. '8, 1930 UNITED STATES PATENT OFFICE NEWTON B. GREEN, OF ROCHESTER, NEW YORK, ASSIGNORYTO EASTMAN, KODAK COMPANY, OF. ROCHESTER, NEW YORK, A CORPORATION OF NEW YORK LIGHT CONTROL FOR PHOTOGRAPHIC-I PRINTING MACHINES Application filed December 31, 1926. Serial No. 158,340.

This invention relates to photography and more particularly to photographic printing machines; and it has for its obj ect to provide a means for accurately determining the actinic light value passed from a lamp to a printing panel; to provide such a device I which will function properly during fluctuations in line voltage as well as when the line voltage is constant; to provide a device of the character described which may be built into a printer or which may be built as a unit to operate with printing machines already on I the market; andother objects will appear hereinafter from the following specification,

the novel features being pointed out inthe claims at the end thereof. a

The electric motors hitherto available for photogra hic timers and printers have not had spec -voltage characteristics analogous to the actinic light-voltage characteristics of modern printing lamps. In general, the speed has approximately varied .as the first power'of the voltage; and always substantially less than the third power, so far as I am aware.

An electric motor, especially designed for me, has now become available with its speed varying about as the fifth power of the voltage. This motor, per se, is not claimed herein.

Coming ow to the drawings wherein like reference characters denote like parts throughout:

Fig. 1 is an example of a printer including a light control constructed in accordance with and illustrating one vention;

Fi 2 is a chart showing motor speed characterlstics under diiferent voltage changes;

Fig. 3 is a part section, part side elevation of a printer into whith a second embodiment of my invention has been built I Fig. 4 is a fragmentary detail of front elevation, part of the timing mechanism;

Fig. 5 is a fragmentary detail, part in section and part a side elevation of part of the timing mechanism and 4 Fig. 6 is a perspective of the timing scale used on the machine shown in Fig. 1.

In the first embodiment of my invention the printer may consist of a housing or box 1,

embodiment of my in standing on a base 2 and supporting a bracket 3 to which a link 4, of the toggle 5 is pivoted. The other toggle link ,6 is pivoted at 7 to a platen 8 and is extended at 9 to carry a handle 10. Platen 8 is pivoted at 11 to the printer. The printer top 12 may have the usual printing panel 13 beneath which there is a reflector 14 carrying a printing lamp 15 and pilot lamp 16 in the usual manner.

Each time theplaten is lowered the lamp 15 burns, as the circuit is closed by spring switch 17 under the force of arm 18 and through wiring to be hereinafter described. Pilot lamp 16 preferably burns continuously.

Referring to Fig. 2, the chart indicates in dashed line T a typical motor having, as example, a speed of 3000 R. P. M. at 115 volts.

For each five volts change there is'a. speed i change of roughly 10 per cent, formotormanufacturers have as far as possible designed motors to retain as near a constant speed as possible at the voltages in the vicinity of the voltage for which they were particularly de slgne The line S on this chart is drawn according to the formula a:= k y. If w indicates the candlepower of an incandescent electric lamp, 3; the applied voltage and 7;: a constant of the lamp, this curve illustrates the change in candlepower due to change in voltage. If a: indicates the revolutions per minute of a special motor, 3; the applied voltage, and 7a a constant of the motor, it illustrates the change in speed due to change involtage.

In the present case where 7c=140 109,' it indicates the speed characteristics of a motor in which the speed varies in a much greater proportion with the same changes in voltage than it does in the typical motor, this change being in'the same order of magnitude as the 9 change in actinic lamp brightness due to similar voltage variation.

In the first embodiment of my invention I show the means for determining the time during which actinic light reaches the panel, Fig. 1 to consist of a motor S M connected to turn a commutator 20 through shaft 21, worm 22 and gear 23. The commutator is mounted on a shaft 24 supported by bracket 26. It includes an insulated drum 2,7 in which a metallic contact piece 28 is inserted. At each revolution of the commutator 20 the circuit is momentarily made through contacts 29 and 30.

A lamp 31, preferably of dark or nonactinic color such as red or amber is mounted on the bracket 32 on the printer top where it may be easily observed by the operator. This lamp is under control of commutator 20 and flashes in the present embodiment once for each revolution thereof. These flashes may be arranged at any convenient time interval :11- though I prefer about two a second at normal voltage since these may be easily counted.

The circuit is as follows; the line wires'34 35 come into the printer at 36, wire 34 being broken by a switch 37 from which it goes to one side of the pilot lamp at 38, one motor terminal 39 to one contact of the commutator, and to one printing lamp terminal 42. The other wire is broken by spring switch 17 and thence to one side 40 of lamp 31 and tity for a given number of flashes is always the same as changes in voltage merely cause motor S to change. speed and as this speed change corresponds with the actinic'brightness change in the lamp 16 the same quantity of light rays may be delivered to the print.- ing panel.

This is a simple application of my invention well adapted to be, either built into a machine or to be furnished as a unit which 'may be added to printers already on the market.

. If desired a printer may be operated by a timing mechanism a typical example of such a machine being shown in Figs. 3 to 6 inclusive where a second embodiment of my invention is shown.

Here the means for determining the actinic light passing to the printing panel is mechanically connected to operate the platen whereas in the first embodiment the platen was moved by the operator guided by a visiblesignal.

Thus the determining means may or may not be mechanically connected to the platen. In the embodiment of my invention illustrated in Figs. 3 to 6 the printer comprises a frame 50 su porting a top 51 in which a printing pane 52 is inserted. A platen 53 1s hinged at 54 to the top and the sections comprising the platen are normally turned about hinge 54 and hinge 55 by springs 56. and 57 into an open position in which the panel 52 is uncovered. A dash pot 58 is preferably employed to cushion the upward movement of the platen.

The platen may be held closed by a spring latch 59 one end 60 of which is attached through a pin and slot connection 61, 62 to the core 63 of a solenoid 64. Obviously when the solenoid is energized the latch 59 is moved to release platen 53 which may then raise under the impulse of springs 56 and 57.

A pilot lamp 65 is connected to burn all the time when the switch 66 is closed, this also .making the circuit for motor S M throu h wires 67 and 68. A printing lamp 69 is a so connected to wire 67 on one side, and to a wire 69' on the other, this wire leading to track 70. A second track 70 lies concentric with 7 O and these tracks may be simultaneously engaged by a contact 71 to make a circuit through wires 67, 69', 72 and 68 to light lamp 69.

The timing mechanism may include a large gear 7 3 meshing' with pinion 74 driven by motor-.S M. Motor S M has the same characteristics as the motor used in the first described embodiment of my invention and has therefore the same designating character.

Gear 73 which is a timing gear turns upon shaft 75 carried by brackets 76 (only one shown). A lever 77 is mounted to turn freely on -shaft 75 and is provided with a latch 78, pivoted at 79 to the handle 80, and having an operating handle 81 and an angular extending arm 82 terminating in a pointer 83.

Latch 78 is adapted to engage teeth 84 of gear 73 (Fig. 4) and may be cammed from the teeth at the zero position by a cam 85 (Fig. 5) this cam also constituting a switch. As the arm is moved by gear 73 in the direction shown by the arrow it strikes switch arm 86 moving it against pressure from spring 87 and making contactwith terminal 88 which is connected by wire 89 to wire 68. As the gear moves arm 77 further the latch .is forced from teeth 84 until the dot and dashed line position is reached, where arm 77 stops, and which position is known as the zero position. Cam 85 (and with it switch 86) may be altered to adjust the throw off of arm 77 through the screws 90 and slots 91.

When the switch 86 momentarily makes a circuit through wires 89, 68 and 92, 67 the solenoid 64 is energized releasing latch 59 and opening the platen.

Arm 82 is attached to plunger 93 which carries a shoe, or contact 71 adapted to form a contact between rails 70 and 7 At the zero position the shoe lies beyond the end of these rails. When, the operating handle 81 lies against handle 80 shoe,71 lies against only one rail 70- (dashed lines Fig. 4) and when latch 78 is engaged between teeth 84 the shoe engages both rails making the circuit for printing lamp 69.

Pointer 83 is adapted to move along an lOO lamp 65 and starting motor S M and timing gear 73. The platen 53 is open and the operator judges his negative over panel 52 by the light from lamp 65 in the usual manner. He then closes the platen by pushing it down beneath latch 59. If the required time is 7 seconds he grasps handles 80 and 81 squeezing them together and moves lever 77 until pointer 8'3 registers with 7 on scale 95. Releasing handle 81 simultaneously engages members 78 with teeth 84 and moves plunger 93 causing shoe 71 to engage both rails 7 0 makin a circuit for lamp 69. Gear 7 3 turns hand e until 78 strikes switch 86. This takes place just after lamp 69 is extinguished by shoe 71 riding off the ends of rails 70. 86 strikes 88 making the solenoid circuit and operating latch 59causing the platen to open. Switch 86 is again released and cam 85 has moved 78 to the zero position.

It should be noted that with both embodiments of my invention the same actinic light is always delivered at the same setting, although the actual duration of the exposure may be materially altered. This automatic means for determining the actinic light passing to the printing panel that is by the motor having characteristics that the speed of the motor changes in substantially the same rates as the actinic value of the printing lamp, is the chief feature of my invention. Obviously it may be applied in practice in many different forms, two of which are fully described hereinabove. scope of my invention all such forms as may come within the terms of the following claims.

Having thus described my inventiomawhat I claim as new and desire to secure byLet- .v ters Patent is:

1. In. a photographic printer, a printing panel, an electric lamp positioned to illuminate said panel, means to measure the period during which said lamp illuminates the panel, an electric motor operating said means in proportion to the speed of themotor, the

speed characteristics of the motor with respect to the voltage applied thereto being a function of at least the third power thereof and being of the same order as the actinic light characteristics of the lamp with respect to the voltage applied thereto, and an electric circuit including said lamp and said motor and a common source of electromotive power whereby the lamp and motor will be subject to proportionate variations in voltage from the common source.

2. In a photographic printing machine, the combination with a printing panel of a platen movably mounted with respect thereto, an

I contemplate as within the electric printing lam the actinic .light from which varies more t an the third power of the voltage through the lamp, means for determining the time during which actinic light from said lamp reaches said panel, an electric motor .for driving said determining means in proportion to the motor spec l,'said motor being connected to have the voltage through it varied at the same time and in the same proportion as through the lamp, the

voltage speed characteristics of said motor be-- ing of the same order as the act1n1c-l1ght-- voltage characteristics of said lamp.

3. In a photographic printing machine, the combination with a printing panel, of a platen movably mounted with respect thereto, anelectric printing lamp, the actinic light from which varies more than the third power of the voltage through the lamp, means for determining the time during which actinic light from said lamp reaches said panel, an electric motor for driving the determining-means in proportion to the motor speed, said motor being adapted to vary in speed more thanthe third power of the voltage through the motor, and connections between said motor and said electric lamp whereby both may be operated from a common source of power.

4. In a photographic printing machine, the combination with a printing panel, of a platen movably mounted with respect thereto, an electric circuit comprising a variable voltage supply of power, an electric lamp connected to said circuit the actinic light of which varies more'than the third power of the voltage passing therethrough, a motor connected to the circuit the speed of which varies in proportion to the actinic light variation of the lamp, and an actinic light determining means adapted to automatically determine the quantity of actinic light passed to the printing panel by the lamp.

5. In a photographic printing machine, the

combination with a printing panel, of a platen 1 movably mounted with respect to the panel,

an electric printing lamp spaced from the panel being adapted to direct actinic light thereto, said lamp being of a type adapted to give different actinic values upon changes in voltage, a source for supplying electric energy at varying voltages, a motor adapted to vary in-speed with changes in line voltage, said variationsin speed being in the same ratio as the variationsin actinic brightness of the lamp, and means under control of said motor adapted to automatically determine the actinic light values passed by the lamp to the printing panel.

6. In a photographic printin machine, the combination of a printing .pane with an electric lamp spaced therefrom, a source of variable voltage power, connections between said source and said lamp, the lamp being of a type in which the actinic value varies more than the third power of the voltage passing therethrough', a motor and connections between the motor and source of power, said motor being adapterlto vary in speed more than the third power of voltage passing therethrough, mechanism adapted to determine a.

time interval for an exposure of light sensltive material to the actinic light from said lamp, ancl connections between said mechanism and motor through which the motor may vary the time interval in accordance with voltage variationsand cause the lamp to emit a predetermined quantity of actinic light to the printing panel.

' Signed at Rochester, New York, this 24th day of December, 1926.

NEWTON B.- GREEN. 

